Epidermal growth factor receptor (EGF-R) regulates the growth of human transitional cell carcinoma (TCC) of the bladder in part, by regulating the expression of the matrix metalloproteinase MMP-9. We observed that therapy of human TCC growing within the bladders of athymic nude mice with the EGF-R inhibitor C225 down-regulated the expression of MMP-9 and inhibited tumor growth and metastasis. The goal of this proposal is to delineate the cellular and molecular mechanisms by which EGF-R directed therapy inhibits MMP-9 expression. Four Specific aims will be pursued. Four specific aims will be pursued. First, we propose to establish that the down-regulation of MMP-9 by EGF-R blockade is common the interruption of signaling and not selective to the type of therapy. We will use alternative strategies of EGF-R selective tyrosine kinase inhibitors and the enforced expression of dominant negative mutant EGF-Rs (mitogenically-active or -inactive). Second, we will analyze rates of transcription, promoter activity, and the cis-trans elements regulating transcription to determine the mechanism for the down-regulation of MMP-9 gene expression following EGF-R blockade therapies. Third, to determine a causal effect of EGF-R signaling on MMP9 production and TCC angiogenesis, we will test the in vitro and in vivo effect of EGF-R blockade on TCC cells engineered to constitutively express MMP-9 as well as strategies designed to specifically block the expression/function of these factors. Finally, we propose to evaluate whether the therapeutic efficacy of cytoreductive chemotherapy is enhanced in combination with EGF-R blockade therapy and whether this therapy will down-regulate MMP-9 expression. We hypothesize that MMP-9 is a relevant target for novel therapy since it is over-expressed by human TCC which resists conventional therapy. The knowledge gained from this research will extend our understanding of the cellular and molecular mechanisms by which EGF-R directed therapy inhibits tumor growth and lead to novel therapies for the advanced TCC by combining conventional cytoreductive chemotherapy with EGF-R inhibitors that will ultimately by translated into clinical trials.